This invention relates to an induction system for an internal combustion engine and more particularly to a tumble control valve for the intake port of an internal combustion engine.
As is well known, most internal combustion engines are called upon, in their application, to operate over widely varying speed and load ranges. This is particularly true in connection with vehicular applications such as automobiles and motorcycles. As is also well known, because of this speed and load variation over which the engine is operated, there are many compromises in the design of the engine. This is particularly true in the area of the induction system.
It has been well known that combustion at low engine speeds and low engine loads can be significantly improved with attendant improvements in fuel economy and exhaust emission control if a high degree of turbulence is induced into the intake charge and in the combustion chamber. However, all turbulence increasing devices in the induction system tend to offer some flow resistance. Therefore, the use of turbulence increasing devices in the induction system reduces the maximum power output of the engine. Thus, most induction systems are designed as compromise between good low speed performance and good high speed performance.
One form of turbulence which is generated in the combustion chamber is characterized as "swirl". Swirl is a flow of the charge in the combustion chamber in a generally circumferential direction around the axis of the cylinder. Swirl is generally generated by use of swirl ports in the induction system. However, the generation of swirl can reduce the volumetric efficiency at high speed. This is because swirl ports have higher flow resistance than non-swirl ports. In addition, there are some phases of running of the engine when swirl is not desirable even though some form of motion of the charge in the chamber is desirable.
Another form of motion in the combustion chamber is called "tumble". Tumble is a swirling motion of the intake charge about an axis that generally extends transversely to the cylinder bore axis. With such a flow arrangement, the charge tends to flow across the cylinder head, down one side of the cylinder bore, back across the cylinder bore across the top of the head of the piston and then up the other side of the cylinder bore back to the cylinder head with this flow pattern repeating. This type of motion also requires the formation of a specially formed port which will provide flow resistance and reduce volumetric efficiency under high speed. Like swirl, tumble is more effective at some speed than other speeds.
Of course, even more turbulence may be generated in the intake charge if both swirl and tumble can be generated at the same time. However, generating both such motions through a single port configuration can further increase the flow resistance and reduce high speed performance.
It is, therefore, a principal object of this invention to provide and improved induction port system that will permit selective increase in turbulence in the combustion chamber under some running conditions and different flow patterns under other running conditions.
It is a further object of this invention to provide an arrangement for the induction system of internal combustion engines which permits the generation of both swirl and tumble.
It is a further object of this invention to provide an induction system for an internal combustion engine wherein swirl and tumble can be generated under some running conditions but avoided under other running conditions.
It is yet another object of the invention to provide an arrangement for the induction system of an engine which permits the generation of swirl and/or tumble, depending upon the running conditions.
One way in which the flow pattern in the combustion chamber can be varied under varying speed and load conditions is to provide a control valve in the induction passage that changes the effective configuration of the induction passage as the control valve is moved. The control valve can then be moved in response to varying speed and load conditions so as to provide the desired flow pattern. Such arrangements, however, as previously proposed have only permitted the establishment of either one type of swirling motion (either swirl or tumble) or substantially no turbulence.
It is, therefore, a further object of this invention to provide a single control valve arrangement that permits the generation of either swirl and/or tumble in the induction system and combustion chamber.
One technique for changing the flow pattern from an intake passage in an internal combustion engine employs an additional passage that intersects the main intake passage upstream of the valve seat and through which another higher velocity flow is established. However, like other flow altering devices, there are some running conditions when it is not desirable to have this small port be effective. This can be done through the provision of a control valve but if another control valve is also employed for changing the effective configuration of the port, then the engine becomes very complicated. Furthermore, it may be physically impossible to employ two such valves in the cylinder head of an engine, where the intake port is normally formed.
It is, therefore, a still further object of this invention to provide an improved control valve arrangement for an engine induction system wherein the flow through two ports terminating at a common valve seat may be controlled by a single valve element to alter the flow relationship of the charge entering the combustion chamber.
As has been noted, one way in which the flow patten within a combustion chamber may be altered is by providing a control valve that operates in the intake passage of the engine. However, where such a control valve is provided, even when the control valve is in a wide open position, some obstruction to the flow through the intake passage may occur. This can be either by direct flow resistance of the valve or a mounting portion of it extending into the induction passage even when the valve is fully opened. In addition, the control valve in its fully open position or some portion associated with it can give rise to a less than smooth intake passage which will induce turbulence within the intake passage itself and, accordingly, adversely effect volumetric efficiency.
It is, therefore, a still further object of this invention to provide an improved intake passage and control valve arrangement therefore wherein the effective cross sectional area of the intake passage may be changed but in its fully open position the control valve does not interfere in any way with the smooth transition of flow through the intake passage.
It is a further object of this invention to provide an improved intake passage and control valve arrangement for an internal combustion engine.
In connection with the control of the flow pattern of an intake charge into the combustion chamber from an intake port, there may some advantages in utilizing a rectifier plate in the intake port upstream of the valve seat so as to direct the flow. In addition, a control valve may be employed in conjunction with such a rectifier plate so as to not only control and direct the flow but change the velocity and direction.
It is, therefore, a still further object of this invention to provide an improved intake port and rectifier structure.
In connection with the use of such a rectifier plate in the intake passage, there is also a problem in actually forming such a plate in the cylinder head. If an attempt is made to cast the port directly into the cylinder head, this can greatly complicate the casting process and, in fact, may cause other problems. If a separate insert is employed, however, then there is a risk that the insert may become displaced, particularly during running of the engine.
It is, therefore, a still further object of this invention to provide an improved valve seat and rectifier plate formed as a unitary assembly.
In connection with the use of a control valve for controlling and altering the flow through an intake port, the control valve can be subject to heating during operation of the engine. If there are too large a temperature gradient created between the control valve and the supporting portion of the cylinder head, binding in the control valve operation may result.
It is, therefore, another still further object of this invention to provide an improved arrangement for cooling the control valve of an engine induction system.
It is a further object of this invention to provide an improved cooling arrangement for an intake port control valve that is mounted for rotation in the cylinder head of an engine.
There are a number of advantages to employing rotary control valves for the intake passage of an internal combustion engine. Where the engine has overhead valves, it is also desirable to have the rotational axis for the control valve extend transversely to the intake passage, and if multiple cylinders are employed, to extend along the length of the engine so all intake passages can be controlled by a single valve assembly. However, when this is done, the added components to the cylinder can present problems in connection with placement and operation.
It is, therefore, a still further object of this invention to provide an improved arrangement for affixing a cylinder head and cylinder block together and locating a control valve for the intake passages of the engine without interference from the fasteners.
The problems in placement of the control valves in the cylinder head are further magnified if the engine employs twin overhead camshafts, as is typical with high performance engines. That is, with normal camshaft placements the addition of a control valve for the intake port and the fastening arrangements can give rise to some problems.
It is a further object of this invention, therefore, to provide an improved control valve layout for the intake ports of a twin overhead camshaft internal combustion engine.